2025 OCR A Level Chemistry B (Salters) H433/03 Practical skills in chemistry
Combined Question Paper & Final Marking Scheme
Oxford Cambridge and RSA
Friday 20 June 2025 – Morning
A Level Chemistry B (Salters)
H433/03 Practical skills in chemistry
Time allowed: 1 hour 30 minutes
*1849668194*
You must have:
• the Practical Insert (inside this document)
• the Data Sheet for Chemistry B
You can use:
• a scientific or graphical calculator
• an HB pencil
* H 4 3 3 0 3 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined page at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 60.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 16 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2025 [601/5371/4] OCR is an exempt Charity
DC (PQ/CT) 344775/3 Turn over
, 2
1 This question is about the properties of some Group 2 alkaline earth metals and their compounds.
(a)
(i) The term ‘alkaline’ refers to oxides and hydroxides of the Group 2 elements.
Explain why calcium oxide is described as alkaline.
Include an appropriate equation.
Explanation: .....................................................................................................................................
..........................................................................................................................................................
Equation:
[2]
(ii) Explain why the Group 2 elements are known as s block elements.
..........................................................................................................................................................
......................................................................................................................................................[1]
(b) Strontium sulfate is used in fireworks. Strontium gives a red colour when ignited.
A frequency of red light from the strontium spectrum is 4.62 × 1014 Hz.
Calculate the energy per mole of photons of this frequency in kJ mol–1.
Give your answer to an appropriate number of significant figures.
Energy = ........................................... kJ mol–1 [3]
© OCR 2025
, 3
(c) Barium sulfate is very insoluble in water.
(i) Solutions containing sulfate ions give a white precipitate with barium chloride solution.
Write an ionic equation for the formation of this white precipitate.
Include state symbols.
[1]
(ii) A solution has [SO4 2–] = 0.10 mol dm–3.
Calculate the smallest [Ba2+] in the solution which will just give a white precipitate.
For barium sulfate, Ksp = 1.0 × 10–10 mol2 dm–6.
[Ba2+] = .......................................... mol dm–3 [2]
(d) Calcium and potassium are in the same period of the periodic table.
Explain why calcium has the higher melting point.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
......................................................................................................................................................[2]
© OCR 2025 Turn over
, 4
(e) * A group of students use the apparatus below to show the trend in thermal stability of the Group 2
carbonates.
Clamp Delivery tube
Group 2 carbonate Lime water (calcium
hydr oxide solution)
Heat
Describe how the students should use this apparatus safely to show the trend.
Describe the observations that the students should obtain and explain the theory behind these
observations.
..........................................................................................................................................................
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..........................................................................................................................................................
......................................................................................................................................................[6]
© OCR 2025
Combined Question Paper & Final Marking Scheme
Oxford Cambridge and RSA
Friday 20 June 2025 – Morning
A Level Chemistry B (Salters)
H433/03 Practical skills in chemistry
Time allowed: 1 hour 30 minutes
*1849668194*
You must have:
• the Practical Insert (inside this document)
• the Data Sheet for Chemistry B
You can use:
• a scientific or graphical calculator
• an HB pencil
* H 4 3 3 0 3 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined page at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 60.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 16 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2025 [601/5371/4] OCR is an exempt Charity
DC (PQ/CT) 344775/3 Turn over
, 2
1 This question is about the properties of some Group 2 alkaline earth metals and their compounds.
(a)
(i) The term ‘alkaline’ refers to oxides and hydroxides of the Group 2 elements.
Explain why calcium oxide is described as alkaline.
Include an appropriate equation.
Explanation: .....................................................................................................................................
..........................................................................................................................................................
Equation:
[2]
(ii) Explain why the Group 2 elements are known as s block elements.
..........................................................................................................................................................
......................................................................................................................................................[1]
(b) Strontium sulfate is used in fireworks. Strontium gives a red colour when ignited.
A frequency of red light from the strontium spectrum is 4.62 × 1014 Hz.
Calculate the energy per mole of photons of this frequency in kJ mol–1.
Give your answer to an appropriate number of significant figures.
Energy = ........................................... kJ mol–1 [3]
© OCR 2025
, 3
(c) Barium sulfate is very insoluble in water.
(i) Solutions containing sulfate ions give a white precipitate with barium chloride solution.
Write an ionic equation for the formation of this white precipitate.
Include state symbols.
[1]
(ii) A solution has [SO4 2–] = 0.10 mol dm–3.
Calculate the smallest [Ba2+] in the solution which will just give a white precipitate.
For barium sulfate, Ksp = 1.0 × 10–10 mol2 dm–6.
[Ba2+] = .......................................... mol dm–3 [2]
(d) Calcium and potassium are in the same period of the periodic table.
Explain why calcium has the higher melting point.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
......................................................................................................................................................[2]
© OCR 2025 Turn over
, 4
(e) * A group of students use the apparatus below to show the trend in thermal stability of the Group 2
carbonates.
Clamp Delivery tube
Group 2 carbonate Lime water (calcium
hydr oxide solution)
Heat
Describe how the students should use this apparatus safely to show the trend.
Describe the observations that the students should obtain and explain the theory behind these
observations.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
......................................................................................................................................................[6]
© OCR 2025
